The full sentence would be:
It is like something my mother wore thirty years ago.
The correct contraction of <em>it is </em>is <em>it's.</em>
The answer is B. It's like something my mother wore thirty years ago.
Since you have it, why not take some points ;3
A prepositional phrase starts with a preposition. Although after can be used as a preposition, in this case it is an adverb, and is followed by a clause, not a phrase. The correct answer is thus to the movies, because the phrase starts with the preposition to.